Scientific Publications - Work Done by Microbiology Reader Bioscreen C

Martin Antonsen, Carbohydrate fermentation by non-starter lactic acid bacteria isolated from danbo cheese, Food Congress 2002, Future Food a scientific perspective - January 16-17 2002 at Danish Technical University - DTU, Posters - abstracts on-line, 1 pp.

ABSTRACT

Non-starter lactic acid bacteria (NSLAB) are adventitious LAB occurring in semi-hard cheese during maturation. In Scandinavian cheeses these mainly belongs to the genus Lactobacillus. The carbohydrate(s) utilised by NSLAB for growth in the maturing cheese has not yet been identified. To generate knowledge of NSLAB growth in cheese, the growth of 41 NSLAB isolated from Danbo on carbohydrates possibly released by lysed cells of starter bacteria or from the milk-fat globule membrane was analysed. The NSLAB strains used including 38 Lb. paracasei, 2 Lb. curvatus and 1 Lb. casei. Sugar fermentation profiles were recorded using API 50 CH tests. The growth of NSLAB on glucose, lactose, galactose, mannose, ribose, N-acetylglucosamine (NAG), N-acetylgalactosamine (NGA) or N-acetylneuraminic acid was analysed using Bioscreen C equipment. A carbohydrate restricted base medium containing casitone, Tween 80, phosphate buffer, minerals and vitamins was used, tests were carried out at 24 or 30 C and plates were shaken after every 15 minutes. According to the API 50 CHL database, strains of Lb. paracasei were divided into four groups: Lb. paracasei group I (48 %), Lb. paracasei group II (3 %), Lb. paracasei group III (24 %) and curvatus-like group (24 %). All strains of Lb. paracasei were able to use galactose, glucose, fructose, mannose, N-acetylglucosamine and tagatose. Most strains (more than 70 %) fermented ribose, lactose, mannitol, maltose, esculine, salicine, saccharose, trehalose, melezitose, cellobiose and gluconate. In the Bioscreen C tests 50 % of Lb. paracasei strains were N-acetylgalactosamine positive but no strain fermented N-acetylneuraminic acid. Most strains of the NSLAB fermented glucose, N-acetylglucosamine, mannose, galactose and lactose rapidly. Though, some strains of all tested species fermented lactose and galactose very slowly or not at all. The slowest growth rates of the NSLAB were observed on ribose. Moreover, about half of the Lb. paracasei that were ribose positive according to API 50 CH tests were ribose negative in the Bioscreen C tests. The growth rate on ribose was also compared for some Lb. paracasei strains on agar plates containing 2.5 % NaCl and incubated anaerobically at 12ºC. Most Lb. paracasei strains formed colonies of 1 mm within 2 to 4 weeks under cheese like conditions. The strain differences in growth rate on ribose did not completely agree with the results from the Bioscreen C. NSLAB isolates grow faster on the different hexoses used than on ribose. However, further studies are required regarding the availability of these hexoses in maturing cheese.

(Abstract online - Eston.l.)

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Last modified: May 25, 2005